Margaret Osborne duPont (born Margaret Evelyn Osborne; March 4, 1918 – October 24, 2012) was a World No. 1 American female tennis player.

DuPont won a total of 37 singles, women's doubles, and mixed doubles Grand Slam titles, which places her fourth on the all-time list despite never entering the Australian Championships. She won 25 of her Grand Slam titles at the U.S. Championships, which is an all-time record.

DuPont won six Grand Slam singles titles, saving match points in the finals of the 1946 French Championships (versus Pauline Betz Addie) and 1948 U.S. Championships (versus Louise Brough). In terms of games played, the 1948 final at the U.S. Championships is the longest women's singles final ever played at that tournament (48 games).

DuPont teamed with Brough (later Louise Brough Clapp) to win 20 Grand Slam women's doubles titles, which ties Martina Navratilova and Pam Shriver for the most Grand Slam titles ever won by a women's doubles team. DuPont and Brough won nine consecutive titles at the U.S. Championships from 1942 through 1950. They won that tournament 12 of the 14 years they entered as a team. Their 12 titles is an all-time record for a women's doubles team at the U.S. Championships, easily surpassing the four career titles won by the teams of Navratilova and Shriver, Doris Hart and Shirley Fry Irvin, and Sarah Palfrey Cooke and Alice Marble. DuPont won a total of 13 women's doubles titles at the U.S. Championships, which also is an all-time record, as is her 10 consecutive women's doubles titles at the U.S. Championships from 1941 through 1950.

DuPont won more mixed doubles titles at the U.S. Championships than any other player. She won nine titles, including four with William Talbert (a record for a mixed doubles team at the U.S. Championships) and three with Neale Fraser.

According to John Olliff and Lance Tingay of The Daily Telegraph and the Daily Mail, DuPont was ranked in the world top ten from 1946 through 1950, 1953, 1954, 1956, and 1957 (no rankings issued from 1940 through 1945), reaching a career high of World No. 1 in those rankings from 1947 through 1950.[2] DuPont was included in the year-end top ten rankings issued by the United States Lawn Tennis Association in 1938, 1941 through 1950, 1953, 1956, and 1958. She was the top ranked U.S. player from 1948 through 1950.[3]

From 1938 through 1958, DuPont went undefeated in ten Wightman Cup competitions, winning her ten singles and nine doubles matches. She also captained the U.S. team nine times, winning eight.

DuPont married William duPont, Jr. in 1947 and later interrupted her career to give birth to a son, William III. She was one of the few women to win a major title after childbirth but never played the Australian Championships because her husband would not let her.

They didn't start to invite people down there and pay their expenses until I got married, and that was wintertime and Will's vacation time, and I just never got to go. He threatened to divorce me if I went to Australia, so I never went. He had that respiratory trouble, and he wanted me to come to California with him. He thought I should be with him. That was that.[4]

NH = tournament not held.
R = tournament restricted to French nationals and held under German occupation.
A = did not participate in the tournament.
SR = the ratio of the number of Grand Slam singles tournaments won to the number of those tournaments played.1In 1946 and 1947, the French Championships were held after Wimbledon.

NH = tournament not held.
R = tournament restricted to French nationals and held under German occupation.
A = did not participate in the tournament.
SR = the ratio of the number of Grand Slam singles tournaments won to the number of those tournaments played.1In 1946 and 1947, the French Championships were held after Wimbledon.

NH = tournament not held.
R = tournament restricted to French nationals and held under German occupation.
A = did not participate in the tournament.
SR = the ratio of the number of Grand Slam singles tournaments won to the number of those tournaments played.1In 1946 and 1947, the French Championships were held after Wimbledon.